Recently, in the field of pathology, attention has been focused on virtual slide systems that serve as a substitute for an optical microscope which is a tool for pathological diagnosis and that enable pathological diagnosis to be performed on a display by photographing a sample to be examined (imaging target) which is mounted on a preparation and by digitizing images. By digitizing pathological diagnosis images by using a virtual slide system, optical microscope images of a sample to be examined in the related art can be handled as digital data. As a result, advantages, such as faster telediagnosis, the usage of digital images as an explanatory aid for patients, sharing of rare cases, and more efficient education and training, are expected to be achieved.
To achieve operations using a virtual slide system which are approximately equivalent to those using an optical microscope, it is necessary to digitize the entire sample to be examined which is on a preparation. By digitizing the sample to be examined, digital data generated using a virtual slide system can be observed using viewer software which operates on a personal computer (PC) or a workstation. The number of pixels for the entire digitized sample to be examined is typically several hundreds of millions to several billions, which is a very large amount of data.
The amount of data generated using a virtual slide system is enormous, and various observations can be performed from micro-observation (enlarged detail image) to macro-observation (bird's-eye view of the whole) by using a viewer to perform an enlargement/reduction process, and the system is thus convenient in various different ways. By obtaining all pieces of necessary information in advance, instant display of a low-magnification image to a high-magnification image can be performed using a resolution and a magnification which are desired by a user. In addition, obtained digital data is subjected to image analysis, and, for example, determination of the shape of a cell, calculation of the number of cells, and calculation of the nucleus to cytoplasm area ratio (N/C ratio) are performed. Accordingly, various types of information useful in pathological diagnosis can be also presented.
As such a technique of obtaining a high-magnification image of an imaging target, a method has been proposed in which high-magnification images obtained by photographing portions of an imaging target are used to obtain a high-magnification image of the entire imaging target. Specifically, in PTL 1, a microscope system is disclosed which divides an imaging target into small portions that are photographed, and which combines the images for the small portions thus obtained into a combined image for the imaging target which is displayed. In PTL 2, an image display system is disclosed which obtains partial images for an imaging target by capturing images while the stage of a microscope is being moved and corrects distortions in the images so as to combine the images. In PTL 2, a combined image having unobtrusive connecting regions is generated.